The present invention relates in general to detecting flaws on the disk surface of a magnetic disk storage medium, and, in particular, to a method and apparatus for using the data interface of a disk drive to efficiently identify and characterize disk flaws.
A disk drive typically includes multiple disks that rotate on a spindle. Each disk normally has two surfaces for storing data in generally concentric data tracks. The data can be written onto the disk surfaces and read therefrom by transducer heads that are guided over the disk surfaces by an actuator arm. The actuator arm, in turn, is driven by a voice coil motor controlled by a control system to position the transducer heads relative to the desired data tracks. The disk surfaces, transducer heads, and related circuitry thus define a data interface of the disk drive.
An important part of testing and properly operating a disk drive is detecting disk flaws. Such flaws may be due to a variety of factors such as surface scratches, contaminants on the disk surface, and irregularities in the disk fabrication process, and can interfere with proper data storage and retrieval if not accounted for. For example, the flaws may cause data bits or blocks of data to drop in, drop out, or otherwise be improperly stored or retrieved. Accordingly, disk drives are normally tested to identify disk flaws. Depending on the nature of the flaw, appropriate remedial action may be taken such as by mapping the locations of data bits or data sectors where flaws are identified such that these disk areas may be avoided during operation of the disk drive.
A number of such flaw scanning processes have been proposed. Many of these processes involve writing an analog or digital signal onto the disk surface, reading back the signal and analyzing the read signal to identify flaws. Generally, however, these processes are time consuming, inaccurate, and/or provide little real time flaw characterization information regarding the types of flaws.
One flaw scanning process involves using the data interface to identify flaws by writing a pattern of bits into the user data sectors of a disk data track and then reading the data back from the same user data sectors. The read data can then be compared to the written data in order to identify flaws. The data sectors of the disk can thereby be qualified on a bit-by-bit basis. This flaw scanning information can be transferred between the head and the control chip using the so-called NRZ interface which is essentially an I/O data bus, between the read write channel and the controller. For example, a specified bit line of the NRZ interface can be set to a specified high or low value so as to indicate a flaw, This information can be used by the disk drive control system to develop a flaw map.
Although this flaw scan process is useful in identifying media flaws, it is limited in certain respects. For example, this process has been limited to identifying flaws in the data sectors of disks. Disks normally include servo data wedges which are interspersed between data sectors on a disk surface. The servo wedges include information for, among other things, guiding the heads over the data tracks and synchronizing the data channels to properly read or write data in adjacent data sectors. Flaws can occur in such servo wedges that may interfere with proper data storage and retrieval. Accordingly, it is desirable to identify flaws in the servo wedges as well as the data sectors. Moreover, the flaw scan process described above is limited to identifying media flaws. Consequently, in real time, a media flaw can generally be identified but not further characterized. Flaw characterization in the noted process also requires multiple passes over the disk area under analysis which slows the testing process and, in the context of flaw scanning in connection with the manufacturing process, this slows production rates.
The present invention is directed to a method and apparatus for using the data interface to efficiently and accurately identify and characterize flaws on a disk surface. The invention allows for flaw characterization in substantially real time, thereby reducing the time required for flaw testing. In addition, the invention provides an interface for transferring both flaw identification and flaw characterization information between the transducer heads and the controller for substantially complete and accurate flaw detection. The invention also allows for reading flaw scan information from servo wedges as well as user data sectors of the disk. Moreover, in accordance with the present invention, the flaw scan data can be read from the servo wedges and user data sectors in a single pass so as to further decrease testing time. According to one aspect of the present invention, data read from a disk area in a single pass is used to both identify and characterize a disk flaw. The associated method includes the steps of: writing information to the disk area; reading information from the disk area on a single pass over the disk area; based on the read information, identifying a disk flaw and characterizing the disk flaw as to type; and communicating the flaw type to a controller of the disk drive. For example, the flaw may be characterized as being one of a thermal asperity related flaw, Viterbi related flaw, a voltage gain amplifier (VGA) related flaw, a phase-lock loop (PLL) related flaw, or other type of flaw as described in more detail below. This flaw information can be used for disk diagnostics such as in constructing a flaw map for use in operation of the disk drive.
According to another aspect of the present invention, data read from a disk area in a single pass is used to identify and characterize flaws of different types. The corresponding method involves: writing information onto the disk area; reading information from the disk area on a single pass; based on the read information, identifying a first disk flaw of a first type and identifying a second disk flaw of a second type; and communicating flaw information regarding the first flaw type and the second flaw type to a controller of the disk drive. By virtue of this process, flaws of different types can be identified and characterized based on a single pass over a disk surface area.
According to another aspect of the present invention, data read from a disk area in a single pass is used to identify and characterize flaws of different types. The corresponding method involves: writing information onto the disk area; reading information from the disk area on a single pass; based on the read information, identifying a first disk flaw of a first type and identifying a second disk flaw of a second type; and communicating flaw information regarding the first flaw type and the second flaw type to a controller of the disk drive. By virtue of this process, flaws of different types can be identified and characterized based on a single pass over a disk surface area.
According to a still further aspect of the present invention, a process is provided for using the disk drive data interface between the transducer heads and the disk drive controller to transmit flaw scan information sufficient to identify and characterize a disk flaw. The process involves defining a multiple bit data interface assigning a value to at least one bit of the data interface so as to identify a flaw type, and transmitting the value between a read channel and a controller of the disk drive. Preferably, the data interface is populated with at least one bit for providing information regarding a first flaw type and at least another bit for providing information regarding a second flaw type. In one embodiment, a byte wide interface is defined including eight defined bits for providing eight different types of flaw information. Separate bit definitions may be provided for servo wedge addresses and user data sector addresses. In this regard, when the data is presented, the associated procession determines whether it is for a user data sector or a servo wedge, e.g., based on the associated disk address/location.
According to a still further aspect of the present invention, a process is provided for using the disk drive data interface between the transducer heads and the disk drive controller to transmit flaw scan information sufficient to identify and characterize a disk flaw. The process involves defining a multiple bit data interface assigning a value to at least one bit of the data interface so as to identify a flaw type, and transmitting the value between a read channel and a controller of the disk drive. Preferably, the data interface is populated with at least one bit for providing information regarding a first flaw type and at least another bit for providing information regarding a second flaw type. In one embodiment, a byte wide interface is defined including eight defined bits for providing eight different types of flaw information. Separate bit definitions may be provided for servo wedge addresses and user data sector addresses. In his regard, when the data is presented, the associated processor determines whether it is for a user data sector or a servo wedge, e.g., based on the associated disk address/location.